1. Field of the Invention
The present invention relates to a blood collection assembly having safety elements for safe and convenient handling. More particularly, the present invention relates to a blood collection assembly which is adapted for retraction of the needle based on forces of gravity.
2. Description of Related Art
Disposable medical devices having piercing elements are typically used for administering a medication to or withdrawing a fluid from a patient, such as blood collecting needles, fluid handling needles and assemblies thereof. Current medical practice requires that the fluid containers and needle assemblies used in such systems be inexpensive and readily disposable. Consequently, existing blood collection systems, for example, typically employ some form of durable, reusable holder on which detachable and disposable needles and fluid collection tubes may be mounted. A blood collection system of this nature can be assembled prior to use and then disassembled after use.
A popular design configuration of conventional blood collection systems includes a double-ended needle assembly, an evacuated collection tube, and a holder for maintaining the needle assembly and the collection tube in fixed relation. The double-ended needle assembly has a bore extending through a cannula and a hub near a central region thereof. The evacuated fluid collection tube includes a puncturable stopper at one end thereof. In this type of blood collection system, the holder typically has a housing at one end thereof for receiving the needle assembly. Likewise, the holder also has a hollow body with an opening at an opposite end thereof for receiving the collection tube. The needle assembly is rigidly received within the housing of the holder such that a first end of the needle, i.e., the patient end, extends forwardly of the holder for puncturing a vein of a patient. The opposite, second end of the needle, i.e., the non-patient end, extends into the hollow body of the holder. Upon assembly of the blood collection system, the needle assembly is inserted into the housing and the collection tube is inserted through the open end of the hollow body until the second end of the needle pierces the puncturable stopper of the collection tube, thereby allowing fluid communication between the interior of the collection tube and the bore which extends through the needle assembly. To draw a blood specimen from a patient using one of these blood collection systems, the evacuated collection tube is partially inserted into one end of the holder, the first end of the needle is inserted into a patient's vein, and the collection tube is fully inserted into the holder such that blood will be drawn through the bore of the needle assembly and into the fluid collection tube. After drawing the specimen, the collection tube is removed so that the blood contained therein can be analyzed and the needle assembly is detached for disposal.
In addition to being capable of accommodating blood collection tubes, the holders of some fluid transfer systems are compatible with fluid containers having a fluid to be injected into a patient. Thus, such holders can be used to inject fluid into, as well as draw blood specimens from, a patient.
Traditionally, needle holders for such blood collection assemblies have been re-usable, with the needle assembly detached from the needle holder after use, and a new needle assembly attached to the needle holder for re-use thereof, often for use with a new patient. For example, U.S. Pat. No. 6,306,118 discloses a needle holder assembly for use with a separate double-ended blood collection needle which can be easily engaged to and disengaged from the holder through a trigger arrangement, providing for release of the needle from the holder and into a separate sharps container. Similar needle holders which are adapted for quick release and separation of the needle from the needle holder into a separate container are disclosed in U.S. Pat. Nos. 4,942,881; 4,984,580; 5,117,837; 5,143,083; 5,299,687; and 5,755,673. Re-use of a needle holder with different needle assemblies provides the possibility of contamination, such as blood spatter within the needle holder.
Moreover, in order to reduce the risk of incurring an accidental needle-stick wound, protection of the used needle tip becomes important. With concern about infection and transmission of diseases, methods and devices to enclose the used disposable needle have become very important and in great demand. Arrangements have been designed for protecting used needle tips involving retracting the needle within the needle holder with the entire device including the needle holder and the needle assembly being disposed of together. For example, U.S. Pat. No. 5,810,775 to Shaw discloses a collection assembly which provides for retraction of the intravenous needle at the patient end of the assembly, and further discloses a hinged cap at the open end of the housing of the holder. After drawing a specimen into a collection tube, the collection tube is removed, and the hinged cap is closed over the opening of the holder, thereby activating the spring-based needle retraction and blocking access to the second end of the needle at the non-patient end. Activation of the hinged cap and the spring-based retraction mechanism requires substantial manipulation by the user and cannot be conveniently accomplished with a single hand, as is ideal for typical phlebotomy practice.
U.S. Patent Application Publication No. 2003/0040717 discloses a retracting needle safety device in which a retraction assembly including a double-ended needle cannula with a patient tip at one end and a non-patient tip at an opposed end is retracted within a tubular body of a needle holder housing after use. The retraction is accomplished through a spring mechanism which biases the retraction assembly into the body of the needle holder housing to contain the needle entirely therein in a manner which is offset from the general axis of the housing.
U.S. Patent Application Publication No. 2003/0093009 also discloses a needle safety device with a double-ended needle cannula having a patient tip at one end and a non-patient tip at an opposed end, with the needle cannula permanently mounted to a housing for accommodating an evacuated blood collection tube. A spring propels a safety shield to a shielding position covering the patient tip of the needle cannula upon activation, which is accomplished passively when a tube is inserted within the housing by the tube contacting a latch which releases the shield.
Such prior art retractable needle assemblies and releasable needle assemblies include complex mechanisms for activation, with many relying on spring biasing forces for forced retraction into the attached needle holder housing, or for separation from the housing into a separate container for storing of used needles or sharps.